Cellulose ester film, protective film for a polarizing plate of liquid crystal display and production method of cellulose ester film

DETAILED DESCRIPTION OF THE INVENTION Film for liquid crystal displays is comprised of cellulose ester film, as well as fine particles.
The average diameter of said fine particles is commonly between 0.
05 and 3.
0 .
mu.
m, and is preferably between 0.
05 and 2.
0 .
mu.
m.
Further, in the region of a depth of 10 .
mu.
m from the surface of cellulose ester film, 5 to 500 fine particles, having an average diameter of 0.
05 to 3.
0 .
mu.
m per 1,000 .
mu.
m.
sup.
2, exist in the cross-section of the cellulose ester film.
The thickness of said cellulose ester film is commonly between 20 and 65 .
mu.
m, is preferably between 30 and 60 .
mu.
m, and is more preferably between 35 and 50 .
mu.
m.
Further, said average diameter of fine particles means the average length of particles in the longer axis direction at the observed position of a film, when the cellulose ester film is observed employing an electron microscope and also an optical microscope.
Particles to be observed are not particularly specified, and they may be primary particles or secondary particles which are comprised of coagulated primary particles.
However, particles, which are commonly observed, are mostly secondary particles.
One example of measurement methods is as follows.
An area of 9,775 mm.
sup.
2 of a film is observed employing a microscope, and the average of the particle diameter at the observed position is obtained.
In the same film, the same measurement is carried out at 10 randomly selected positions and each average is obtained.
The average diameter is then obtained by averaging particle diameters at 10 positions.
Further, the number of fine particles in the region of a depth of 10 .
mu.
m from the surface of the cellulose ester film may be determined as follows.
For example, topographic pictures at 10 randomly selected positions per sample film are produced and in each picture, the number of particles in an area of 1000 .
mu.
m.
sup.
2 within a depth of 10 .
mu.
m is determined.
The average diameter of 10 positions is then calculated.
The content of said fine particles, with respect to the cellulose ester of a cellulose ester film, is preferably between 0